I ended up contacting the dealership. It definitely sounds like the engine needs work. Lots of smoke and it is lazy. I was very surprised that they were so forthcoming. No service history, and the engine may need work. It could be nothing, but it may need a rebuild. Not what I need at this time in my life.

I've seen a few nice looking GQs, I've spotted a few 4.2 diesels, turbo and normally aspirated in good nick, but not many 4.8s. Every now and then I am tempted to grab one of the good looking GQs to play with in the mean time... But sensibility prevails. The hunt continues.